<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
    <style>
      body > div {
        width: 200px;
        border: 1px solid red;
        /* 当元素的所有子元素全部浮动后 则自动识别的高度为0 后面的元素会顶上来导致显示异常 添加以下样式解决此问题 */
        overflow: hidden;
      }
      #d1 {
        width: 50px;
        height: 50px;
        background-color: red;
        float: left;
      }
      #d2 {
        width: 50px;
        height: 50px;
        background-color: green;
        float: left;
      }
      #d3 {
        width: 50px;
        height: 50px;
        background-color: blue;
        float: left;
      }
      ul {
        list-style-type: none;
        margin: 0;
        padding: 0;
      }
      li {
        float: left;
        margin-right: 20px;
      }
    </style>
  </head>
  <body>
    <ul>
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    </ul>
    <div>
      <div id="d1"></div>
      <div id="d2"></div>
      <div id="d3"></div>
    </div>
  </body>
</html>
